A thermal transfer film may be used as a donor film upon formation of patterns. The thermal transfer film includes a light-to-heat conversion layer stacked on a base film. A transfer layer including an organic electroluminescent material and the like is stacked on the light-to-heat conversion layer. When the light-to-heat conversion layer is irradiated with light in an absorption wavelength range, the transfer layer can be transferred by the light-to-heat conversion layer. It is necessary for the light-to-heat conversion layer to maintain specific optical density for thermal transfer through light induction, and to have an externally uniform coating for uniform transfer.
In addition, an interlayer may be formed between the light-to-heat conversion layer and the transfer layer. Surface roughness of the interlayer may be an important factor capable of decreasing transfer failure of the transfer layer.
Generally, the base film for the thermal transfer film is a film having coating layer. To impart coatability to the base film, the surface of the base film may be treated with a primer (generally, particles) formed of a material, such as polyurethane, polyester, and the like.
Generally, the thermal transfer film may be prepared into a product through a process of winding the thermal transfer film around a roll. FIG. 3 shows (A) a stack of two thermal transfer films after winding a thermal transfer film 1 around a roll 2 and (B) a thermal transfer film separated therefrom, in a process of preparing the thermal transfer film 1. Referring to FIG. 3, (A) the stack of a first thermal transfer film, which includes a base film 10 having a primer 13 formed thereon, a light-to-heat conversion layer 11 and an interlayer 12, and a second thermal transfer film, which includes a base film 20 having a primer 23 formed thereon, a light-to-heat conversion layer 21 and an interlayer 22, is prepared by winding the thermal transfer film 1 around the roll 2. Here, indentations 14 having a shape of the primer can be formed on the interlayer 12 of the first thermal film due to the primer 23 the base film 20 of the second thermal transfer film by winding pressure of the roll 2.
The indentations 14 can provide poor surface roughness to the interlayer, thereby causing transfer failure of the transfer layer. Although the thermal transfer film including the base film, the light-to-heat conversion layer and the interlayer is illustrated in FIG. 3, the thermal transfer film including the base film and the light-to-heat conversion layer can also suffer from the indentations.